Air circulation systems are incorporated into most building structures. Such air circulation systems typically include air ducts which extend from a central source to regions throughout the building. The central source may include means for heating, ventilating, and/or cooling the air. The air itself is usually forced or blown throughout the system by means of fans or blowers, respectively.
Historically, air ducts have been made of sheet metal. However, those skilled in the art will recognize that sheet metal air ducts contribute to the distribution of unacceptably loud noise. In particular, metal air ducts tend to transmit sound with little or no attenuation, thereby placing an entire building in communication with noise made by the heating, ventilating, and/or cooling equipment, as well as noise made by other operations taking place within the building. A major impact of mechanical noise through duct work is noise that interferes with verbal communications resulting in diminished speech intelligibility in spaces in which verbal communications is a function of the activities within the space. The resulting "noise pollution" can reduce productivity and may, in extreme cases, lead to hearing damage.
One prior art "solution" to the noise problems associated with air ducts has been to line or replace the metal air ducts with fiberglass panels. Those skilled in the art will recognize that fiberglass is suitable for both thermal and acoustical insulation. However, those skilled in the art will also recognize that fiberglass is coming under ever greater scrutiny, being perceived by many as a potential health hazard. The primary concern centers around the fibrous nature of fiberglass relative to the established hazards associated with asbestos fibers.
Although suitable substitutes to fiberglass are being introduced for thermal insulation purposes, the same cannot be said for noise attenuation applications. Thus, a need exists for an air duct and/or an air duct liner which attenuates noise without introducing known health hazards into a building's environment. Ideally, any such air duct and/or air duct liner should comply with current building code requirements and be compatible with current construction methods.